Scalable synthesis of palladium nanoparticle catalysts by atomic layer deposition

Potential applications in drug delivery from nanostructures composed of two oppositely charged polymethacrylates, eudragit^? L100 (EL) and eudragit^? EPO (EE), loaded with three model basic drugs (D), atenolol, propranolol, and metroclopramide were evaluated. The self-organized nanoparticles based on drug-interpolyelectrolyte complexes (DIPEC), (EL-D₅₀)?CEE_X, were obtained by mixing the aqueous dispersions of both polyelectrolytes at room temperature in an ultrasound bath. Dispersions of (EL-D₅₀) neutralized with increasing proportions of EE exhibited a rise of turbidity, particle sizes in the range of 150?C400?nm, and high negative zeta potential. The sign of zeta potential was shifted from negative to positive by changes in composition of DIPEC. Freeze dried DIPEC were easily redispersed in water yielding nearly the same parameters of fresh dispersions. In vitro release experiments using Franz cells showed that DIPEC systems behave as a drug reservoir that slowly releases the drug as water is placed in the receptor compartment. The release rate was raised by ionic exchange with counterions present in simulated physiological fluids placed in the receptor media. Delivery of D from DIPEC exhibited a remarkable robustness toward simulated physiological media of different pH. The DIPEC systems exhibit interesting properties to design nanoparticulate drug delivery systems for oral and/or topical routes.     

Self-assembly and gelation of oxidized glutathione in organic solvents.

The oxidized disulfide form of the ubiquitous tripeptide glutathione (gamma-glu-cys-gly) (GSSG) is shown to produce transparent, thermoreversible gels in aqueous solutions of dimethyl sulfoxide, dimethylformamide, and methanol, at GSSG concentrations as low as 1.5 mM. The gels bind Congo Red and exhibit dramatic green birefringence when observed between crossed polarizers, characteristic of amyloid structures. By transmission electron microscopy, the gels appear to consist of a network of fibrous structures about 75 nm in diameter. Several structurally related peptides, including the glutathione isomer glu-cys-gly and the aspartyl analogue of glutathione (beta-asp-cys-gly), failed to produce gels under similar conditions. These results suggest that the interactions which produce gelation are highly specific and that the unusual peptide geometry introduced by gamma-glu-cys linkage is critical to the gelation behavior. (1)H NMR indicates solvent-dependent perturbation of the gamma-glutamyl alpha- and beta-protons and circular dichroism reveals a shift in the geometry of the disulfide bond under conditions producing gelation. We propose that in appropriate organic solvents, GSSG self-assembles into an extended network of beta-sheetlike structures capable of immobilizing bulk solvent. While obviously speculative, it is interesting to consider possible physiological consequences of glutathione self-recognition in such processes as abnormal protein aggregation and the thiol-disulfide exchange which is believed to participate in protein folding.     

Leveraging Electron Transfer Dissociation for Site Selective Radical Generation: Applications for Peptide Epimer Analysis

Traditional electron-transfer dissociation (ETD) experiments operate through a complex combination of hydrogen abundant and hydrogen deficient fragmentation pathways, yielding c and z ions, side-chain losses, and disulfide bond scission. Herein, a novel dissociation pathway is reported, yielding homolytic cleavage of carbon–iodine bonds via electronic excitation. This observation is very similar to photodissociation experiments where homolytic cleavage of carbon–iodine bonds has been utilized previously, but ETD activation can be performed without addition of a laser to the mass spectrometer. Both loss of iodine and loss of hydrogen iodide are observed, with the abundance of the latter product being greatly enhanced for some peptides after additional collisional activation. These observations suggest a novel ETD fragmentation pathway involving temporary storage of the electron in a charge-reduced arginine side chain. Subsequent collisional activation of the peptide radical produced by loss of HI yields spectra dominated by radical-directed dissociation, which can be usefully employed for identification of peptide isomers, including epimers.

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Fortieth Anniversary of the New Brunswick Laboratory

Research sponsored by the Office of Energy Research, U.S. Department of Energy, under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.     

Temperature-programmed synthesis of micron-sized multi-responsive microgels

A new synthetic protocol for the synthesis of large diameter (2.5 to 5 μm), temperature-, and pH-responsive microgels via aqueous surfactant-free radical precipitation copolymerization is presented. We have found that in this size range, which is not typically attainable using traditional dispersion polymerization approaches, excellent monodispersity and size control are achieved when the synthesis employs a programmed temperature ramp from 45 to 65 °C during the nucleation stage of the polymerization. A combined kinetic and thermodynamic hypothesis for large particle formation under these conditions is described. Particle sizes, volume phase transition temperatures, and pH responsivity were characterized by particle tracking and photon correlation spectroscopy to illustrate their similar behavior to particles made via more traditional routes. These particles have been enabling for various studies in our group where microscopic visualization of the particles is required.     

Environmental exposure to metals of newborns, infants and young children

Anthropogenic emissions, such as those from combustion of fossil fuel, waste incineration and industrial use, contribute to higher levels of metal pollutants, including Cd, Pb and Sb, in the urban environment. These widespread and persistent environmental pollutants have the potential for developmental and reproductive toxicity. Health risks are particularly associated with exposure in utero and the early years of life, since the developing organism is at greater risk from permanent damage, and both absorption and retention can be considerably greater in infants than adults. In order to assess risk to humans, the information on environmental levels of pollutants (environmental monitoring) should be integrated with information on biomarkers of exposure, effect or susceptibility in biological fluids or tissues (biological monitoring). The analysis of tissue from the target organ obtained at autopsy provides a direct record of the accumulation of toxins and allows temporal and geographical trends to be studied. Few literature reports on tissue content of potentially toxic elements include data on newborns and young children since collections of autopsy samples in this age range are rare. Existing data are sometime questionable, because of inadequate sensitivity of the analytical techniques, insufficient control of contamination and lack of validation. Our recent work aimed to establish reliable reference values for the content of Cd, Pb and Sb in the liver of pediatric subjects.